Cressida Bonas "felt a huge responsibility" taking on her new role in 'White House Farm'.

Cressida Bonas

Cressida Bonas

The 30-year-old actress - who stars as Sheila 'Bambi' Caffell in the ITV drama - experienced a rollercoaster of emotions whilst filming the true story of the White House Farm massacre.

She portrays the professional model who was framed for killing her family - including her two young sons and parents - before allegedly committing suicide in 1985, after she was diagnosed as schizophrenic and suffered other mental health issues.

Speaking to the Daily Mirror newspaper, Cressida said: "I felt a huge responsibility. I wanted to make it as honest as I could. Looking at how mental health was treated then, it's so different tot now. The way she was labelled I thought was so shocking. She was a very vulnerable person."

The British beauty described one harrowing scene which stuck with her, as she watched from a window as her character's estranged husband Colin - whose accounts of his family influenced the series - said goodbye to his six-year-old sons, marking the last time he would see them alive.

Cressida added: "I remember everyone on set was really quiet during that filming. I was watching from a window as I wasn't in the scene. That moment really hit me, knowing what was to come. That really stayed with me - I got really emotional. Those are the moments wen this story hits home. This is not fiction. It really happened."

Meanwhile, the actress - who dated Prince Harry from 2012 until 2014 - had been working hard to establish herself as a credible actress over recent years, before earning her biggest role to date.

Cressida previously admitted that her relationship with Prince Harry has stunted her acting career, but she was determined that she wouldn't allow the prejudice to derail her acting dreams.

She said: "It's incredibly frustrating, especially in the industry that I'm in. But you know, it is the way it is ... It's making a stand and saying, 'Actually no, this is who I am, and this is what I want to do.'"